He received the name of Bonaventure in consequence of the exclamation of St. Francis of Assisi (4 October), when, in response to the pleading of the child's mother, the saint prayed for John's [Bonaventure's birth name was Giovanni, John in English] recovery from a dangerous illness, & foreseeing the future greatness of the little John, cried out, "O Buona venture"—"O good fortune!"

Quoth the Holy Family bulletin:

As a boy in Italy, Bonaventure was cured of serious illness through the prayer of St. Francis of Assisi. He later joined the Franciscan Order & taught Scripture & theology. He became a Doctor of the Church. He was known for his intelligence & holiness. He was known to write about the soul's longing for God & God's love for us.

Scripture of the DayMass ReadingsWeekday
The Book of Isaiah, chapter thirty-eight, verses one thru six, twenty-one, twenty-two, seven, & eight;
The Book of Isaiah, chapter thirty-eight, verses ten thru twelve(d) & sixteen;
The Gospel according to Matthew, chapter twelve, verses one thru eight;

He is seen as the miraculous son of Zechariah, an old man, & his wife Elizabeth, who was past the menopause & therefore unable to have children. According to this account, the birth of John was foretold by the angel Gabriel to Zechariah, while he was performing his functions as a priest in the temple of Jerusalem. Since he is described as a priest of the course of Abijah & Elizabeth as one of the daughters of Aaron this would make John a descendant of Aaron on both his father's & mother's families.